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( Younbong Park ) 충남대학교 기초과학연구원 2018 충남과학연구지 Vol.35 No.1
Hydrated europium(III) nicotinate compound has been synthesized and structurally characterized by single crystal X-ray diffraction. The structure is dimeric and then the dimers expand into complex 3D framework through extensive hydrogen bonds between water molecules and N atoms and O atoms in nicotinate ligands. In this dimeric unit there are four bridging and two chelating nicotinate ligands and four water molecules with two Eu<sup>3+</sup> ions. The Eu<sup>3+</sup> ion forms a distorted square antiprism with 8 oxygen atoms around.
Park, Seong-Hun,Oh, In-Hwan,Park, Sungil,Park, Younbong,Kim, Ji Hyun,Huh, Young-Duk The Royal Society of Chemistry 2012 Dalton transactions Vol.41 No.4
<P>This work presents the synthesis, structure determination and magnetic properties of a new complex, phenethylammonium tetrachloromanganate(<SMALL>II</SMALL>), (C<SUB>6</SUB>H<SUB>5</SUB>CH<SUB>2</SUB>CH<SUB>2</SUB>NH<SUB>3</SUB>)<SUB>2</SUB>MnCl<SUB>4</SUB> (Mn-PEA). Single crystals of Mn-PEA were obtained from methanol solution using the solvent-evaporation method at room temperature. The crystal structure of Mn-PEA was determined by single-crystal X-ray diffraction (orthorhombic, space group <I>Pbca</I>, <I>a</I> = 7.2075(9), <I>b</I> = 7.3012(14), <I>c</I> = 39.413(6) Å and <I>Z</I> = 4). The structure consisted of an extended [MnCl<SUB>4</SUB>]<SUP>2−</SUP> network and two phenethylammonium cations to form a two-dimensional halide perovskite structure. Temperature-dependent magnetization measurements indicated that Mn-PEA acted as a weak ferromagnet below <I>T</I><SUB>C</SUB> = 44.3 K due to spin canting. Below <I>T</I><SUB>C</SUB>, the magnetic behavior differed significantly from the behavior commonly observed among weak ferromagnets. The susceptibility depended strongly on the crystal orientation, the external magnetic field strength, and the magnetic history. The isothermal magnetization for two orientations revealed a ferromagnetic moment with a spin-canting angle of 0.04° and a spin-flop transitions with <I>H</I><SUB>sf</SUB> = 3.5 T. The weak ferromagnetism, which manifested as spontaneous magnetization and magnetic hysteresis near a field strength of zero, was driven by interplay between the easy axis and the antisymmetric Dzyaloshinsky–Moriya (DM) interaction, leading to directional dependent magnetic behavior.</P> <P>Graphic Abstract</P><P>Inorganic–organic perovskite (C<SUB>6</SUB>H<SUB>5</SUB>CH<SUB>2</SUB>CH<SUB>2</SUB>NH<SUB>3</SUB>)<SUB>2</SUB>MnCl<SUB>4</SUB> is a 2D canted antiferromagnet with <I>T</I><SUB>C</SUB> = 44.3 K with field-induced spin-flop transition <I>H</I><SUB>sf</SUB> = 3.5 T. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1dt11544h'> </P>
박윤봉 충남대학교 기초과학연구소 1995 忠南科學硏究誌 Vol.22 No.1
The reaction of Cu metal with telluride in the sodium polytelluride flux at 400 ℃ produced the simple two-dimensional [CuTe]^- anionic layer compound with sodium ion as a charge balancing cation. The anionic structure resembles ideal anti-PbO structure. Its synthesis and characterization are discussed in detail.
Milling을 이용한 ZnS:Cu,Cl 형광체의 결정 상 변화 및 EL 특성 연구
이유희,한상도,박윤봉 충남대학교 기초과학연구소 2005 忠南科學硏究誌 Vol.32 No.1
A Green phosphor(ZnS:Cu,Cl) was manufactured by solid-liquid reaction for ELD (Electroluminescence Display). The effect of artificial crystal defect on phosphor surface for the ZnS phase conversion and luminescence efficiency have been studied. It was found that ZnS:Cu,Cl could convert to cubic phase more easily due to the formation of artificial crystal defect on 1st fired phosphor by milling process, resulting in improvement of luminescence of phosphor under the driven EL condition. We found out an optimized milling condition through considering effect of each milling conditions such as milling time and rate on defect. Also we determined relationship between EL emission luminescence and driving conditions. A efficient improvement above 50% was observed in electroluminescence by the artificial defect on ZnS:Cu,Cl phosphors compared to crude phosphor.
Rotational Isomers of N-Alkyl-N-(o-acylphenyl)acetamides
Yeong-Joon Kim,Younbong Park,Kwanghee Koh Park 충남대학교 소재화학연구소 2007 소재화학연구소 논문집 Vol.- No.2
We have studied molecular structure of N-alkyl-N-(o-acylphenyl)acetamides 1?3 by <SUP>1</SUP>H NMR spectroscopy. The <SUP>1</SUP>H NMR spectra clearly displayed that two rotational isomers are present in solution and two geminal N?CH₂ protons are magnetically nonequivalent. This was explained by restricted rotations about both the amide N?CO bond and the aryl-nitrogen bond. The ratios of exo (benzene ring trans to carbonyl) and endo rotamers were estimated to be 6?8:1 from the <SUP>1</SUP>H NMR spectra. The X-ray analysis of N-ethyl-N-(o-benzoylphenyl) acetamide 1 showed that the crystal has exo-form. The rotations about both the amide N?CO bond and the aryl-nitrogen bond were slower on the NMR time scale.
2015 개정 교육과정의 중학교 과학 교과서와 고등학교 화학 교과서의 연계 단원에 사용된 비유의 분석
김민하 ( Minha Kim ),박윤봉 ( Younbong Park ) 충남대학교 기초과학연구원 2021 충남과학연구지 Vol.38 No.1
In this study, we analyzed the analogies used in the interrelated chapters between Middle School Science and High School Chemistry textbooks published under the 2015 revised national curriculum. High School textbooks utilize more analogies than the Middle School textbooks, since the level of the contents gets more difficult moving into upper levels of chemistry textbooks. A frequency analysis of the analogy use shows that the section of “structure of matter” has the highest frequency, while “properties of matter” has the lowest. Most of the analogies are represented in a proper manner, but limitations and clear boundaries of analogies use have not been sufficiently mentioned. Based on these results, educational implications are discussed.
새로운 이차원 구조의 사성분 화합물 KAgBi<sub>2</sub>S<sub>4</sub>의 합성 및 구조 특성 연구
최덕수 ( Duc-su Choi ),박윤봉 ( Younbong Park ) 충남대학교 기초과학연구원 2022 충남과학연구지 Vol.39 No.1
In an effort to search for novel quaternary bismuth sulfide compounds, we have explored K/Ag/Bi/S system and encountered novel quaternary bismuth sulfide compound, KAgBi<sub>2</sub>S<sub>4</sub> using K<sub>2</sub>S<sub>x</sub> molten salt at intermediate temperature. The black hexagonal crystals of KAgBi<sub>2</sub>S<sub>4</sub> are obtained at 350℃ and crystallized in the space group P6<sub>3</sub>/mmc (no.194) with a=4.0216(3)Å, c=30.066(3)Å, γ=120°, Final R<sub>1</sub>/wR<sub>2</sub>=4.37/13.15%. The structure of KAgBi<sub>2</sub>S<sub>4</sub> is composed of negatively charged [M<sub>3</sub>S<sub>4</sub>]<sub>n</sub> <sup>n-</sup> layers separated by charge balancing K<sup>+</sup> ions which are loosely packed in the interlayer spaces.
BaF<sub>2</sub> 용융염을 활용한 Lu<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Ce<sup>3+</sup> 형광체의 광 특성 개선
최강식 ( Kang Sik Choi ),박윤봉 ( Younbong Park ) 충남대학교 기초과학연구원 2020 충남과학연구지 Vol.37 No.1
Greenish yellow Lu<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Ce<sup>3+</sup> (LuAG:Ce) as a conversion phosphor for high-quality light emitting diode (LED) device was prepared through solid state reaction using BaF<sub>2</sub> as a flux. It showed an excellent thermal stability, a high quantum efficiency and a broader photoluminescence excitation spectrum compared with pure LuAG:Ce without BaF<sub>2</sub>. Its improved thermal stability results from the fewer intrinsic defects at high temperature, confirmed by uniformity of surface and size. To evaluate its feasibility for white LED, the LuAG:Ce and commercial Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Ce<sup>3+</sup> (YAG:Ce) were applied to a blue LED with a silicone resin, and their characteristics were compared and analyzed. As a result, the LuAG:Ce phosphor revealed extremely efficient light emission without an efficiency loss under blue LED in comparison with the YAG:Ce phosphor.